PCI: endpoint: Drop superfluous pci_epc_features initialization

struct pci_epc_features has static storage duration, so all struct members
are zero initialized implicitly. Thus, remove explicit zero initialization
for features that are *not* supported so we don't have to touch existing
drivers as new features are added.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
[bhelgaas: squash together, expand commit log rationale]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> #rcar-ep, rcar-gen4
Link: https://patch.msgid.link/20250814152119.1562063-16-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-17-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-18-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-19-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-20-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-21-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-22-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-23-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-24-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-25-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-26-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-27-cassel@kernel.org
Link: https://patch.msgid.link/20250814152119.1562063-28-cassel@kernel.org